Observing the Reaction Kinetics of Sucrose with Polarimetry

Recommended for College.

Introduction

Polarimeters can be used in kinetics experiments to follow the change in concentration of an optically active sample as a reaction proceeds. Sugars are common examples of optically active compounds. Sucrose is a disaccharide that can be broken down into its two substituent monosaccharides, glucose and fructose.

This process occurs too slowly in water to be monitored on any real time scale, so a catalyst, acid or enzyme, must be added to accelerate the reaction rate. In this experiment, hydrochloric acid is used to catalyze the reaction while its rate is monitored using a polarimeter. The experiment will be repeated using the enzyme invertase to catalyze the reaction.

Objectives

In this experiment, you will

Calculate the specific rotation of sucrose using a Polarimeter.

Observe the cleavage kinetics of sucrose with an acid catalyst, hydrochloric acid.

Observe the cleavage kinetics of sucrose with an enzyme catalyst, invertase.

Calculate the rate constant for each run from the rotational readings.